UMD Theses and Dissertations
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Item QUANTIFYING NITROUS OXIDE AND METHANE FLUXES USING THE TOWER-BASED GRADIENT METHOD ON A DRAINAGE WATER MANAGED FARM ON THE EASTERN SHORE OF MARYLAND(2022) Zhu, Qiurui; Davidson, Eric A.; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Excess nitrogen resulting from agricultural fertilizer and manure applications on the Eastern Shore degrades the Chesapeake Bay's water quality and causes environmental issues such as algal blooms and "dead zones". Drainage water management (DWM) is an effective best management practice (BMP) to reduce hydrological nitrate export from croplands to surface and ground water by controlling the timing and the amount of ditch discharge and retaining water within ditches and adjacent fields using drainage control structures (DCS). While promoted denitrification in the subsurface and reduction in nitrate leaching are intended consequences of maintaining higher water table level, an unintended environmental consequence is possible production of nitrous oxide (N2O) from denitrification and methane (CH4) from methanogenesis, which are both potent greenhouse gases (GHGs). Whether the application of DWM leads to a "pollution swapping" concern (i.e., trading reduction of nitrate concentrations in ditch water for increases in emissions of N2O and CH4 to the atmosphere) is a question that must be addressed before more widespread implementation of DWM can be endorsed. In this dissertation, I employed a micrometeorological method called the flux gradient (FG) method to a corn-soybean rotation agricultural system with DCS in eastern Maryland on the Delmarva Peninsula to answer this question. This method was chosen because it allows near-continuous measurements of soil trace gas exchanges at multiple locations with a single laser spectrometer at a fine temporal resolution without disturbing the microclimate between soils and the atmosphere. Soil N2O and CH4 fluxes were quantified using the FG method on this drainage water managed farm for three consecutive years when no fertilizer, synthetic fertilizer, and biosolids were applied in 2018 (soybean), 2019 (corn), and 2020 (corn), respectively. Statistical tests indicated that there were no consistent treatment effects of DWM on soil GHG emissions between DWM and non-DWM conditions, suggesting that DWM did not trade the intended consequence of reduced nitrate leaching for the unintended consequence of increased soil GHG emissions. The biosolid addition in 2020 led to the largest N2O emissions among the three years, while the lowest N2O emissions in the growing season were found in the unfertilized soybean year of 2018. In contrast, different fertilization regimes did not yield distinct differences between the three years for CH4 fluxes. In addition, some potential methodological concerns associated with this tower-based micrometeorological approach were addressed and resolved, conferring confidence that the FG method can be applied simultaneously to multiple plots for N2O and CH4 measurements. This research adds to the existing understanding of the impacts of DWM on soil GHG emissions and suggests that this BMP could be applicable in other regions of the Chesapeake Bay as well as other watersheds. This work also contributes to the efforts of studying the impacts of soil organic amendments on soil GHG emissions and deriving improved estimates of emission factors (EFs) for organic amendments.Item ENHANCING BIOREMEDIATION OF TCE-CONTAMINATED GROUNDWATER AT THE BEAVERDAM ROAD LANDFILL(2022) Saffari Ghandehari, Shahrzad; Kjellerup, Birthe; Torrents, Alba; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Trichloroethene (TCE) is one of the most frequently found groundwater contaminants, thus remediating TCE-contaminated groundwater bodies is crucial in providing safe drinking water to people around the world. However, due to the resistance of its intermediates to degradation and their toxicity, TCE bioremediation is still challenging. Years after the installation of a permeable reactive barrier (PRB), the levels of toxic TCE dechlorination intermediates had increased downgradient from the PRB, indicating the need for actions to prevent the contaminated water from reaching a stream nearby. A review of the reports and monitoring results showed that low groundwater residence time and low pH levels were contributing to the inefficiency of the PRB. A trench was purposed to be installed upgradient from this PRB to increase the groundwater contact time with the microorganisms and organic carbon content of the soil using wastewater biosolids, limestone, and biochar to increase the buffer capacity of the soil and the sorption of TCE to the soil. Bench-scale studies were conducted with biosolids and limestone to observe the effect of the biosolids microbial population on a TCE-dechlorinating mixed microbial community. Both dechlorinating bacteria and methanogens use hydrogen in their metabolism and potentially can compete with each other. While biosolids-limestone reactors produced significantly higher concentrations of methane, the activity of methane-producing microorganisms did not adversely affect TCE dechlorination. Furthermore, the characterization of the microbial community of the reactors indicated the positive effect of biosolids. Based on the results from this study, the trench was installed in January 2020 at the site. The sampling and monitoring results nine months after its installation indicated that the trench filling material had positively affected the soil microbial community and decreased the TCE levels downgradient from the trench. To further characterize the microbial community of the site, passive samplers using biochar were installed upgradient and inside the PRB to compare the activity of the dechlorinating bacteria. It was shown that the PRB microbial population was capable of complete dechlorination of TCE, while dechlorinating bacteria detected in the upgradient samples were not active, resulting in the different TCE concentrations observed in these locations. Overall, the study showed that biosolids can be used as an amendment in the TCE bioremediation purposes. Future work should focus on further monitoring the effect of the treatments, applied in this site.Item INVESTIGATING COMPOSTING AS A METHOD FOR REDUCING ESTROGENICTY IN POULTRY LITTER AND BIOSOLIDS(2015) Hammett, Kirsten; Yonkos, Lance; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Biosolids and poultry litter contain the natural estrogens 17β-estradiol and estrone, which can be transported to receiving waters via runoff when these materials are used as fertilizers. Estrogens are of concern because of their ability to act as endocrine disruptors and feminize fish. In this study, In-Vessel Aerated and Turned composting was investigated for its efficacy at mitigating estrogen concerns in BS and PL. Pre- and post- composted, BS and PL samples were investigated for total estrogenicity and estrogen species concentrations. In addition, conversion of estrone to 17β-estradiol was investigated by measuring the creation of deuterated 17β-estradiol from a deuterium-labeled estrone stock within aqueous PL mixtures. Data from these studies indicates that there may be efficacy in composting BS and PL prior to land application and suggest that estrone is capable of converting to the more potent 17β-estradiol species as a result of entering microbially active environments.Item Temporal Trends of and Influence of Storage Methods on Concentrations of Perfluoroalkyl Substances in Limed Municipal Wastewater Biosolids(2014) Armstrong, Dana Lynne; Torrents, Alba; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Perfluoroalkyl substances (PFASs) are a classification of anthropogenic chemicals used in a variety of consumer and industrial products. Compounds from two PFAS subgroups, perflurocarboxylic acids (PFCAs) and perfluorosulfonic acids (PFSAs) are known to be persistent and have been detected in environmental and biotic samples worldwide. While long-chain PFCAs and PFSAs have been in a phase-out process within the United States and some have been regulated in Europe, these compounds have continued to be produced in developing countries. The sustained use of PFCA and PFSA compounds in consumer products, as well as the ability of some PFASs to degrade into these compounds, has led to their presence in the wastewater treatment (WWT) process. This study analyzes archived limed biosolids from a municipal WWT plant for temporal trends of 8 PFCAs and 4 PFSAs over an eight year period. This study also compares storage methods to determine influence on PFCA concentrations.Item FATE OF BACTERIAL AND VIRAL INDICATORS IN AN ADVANCED WASTEWATER TREATMENT PLANT(2013) Liang, Chung-Che; Wigginton, Krista R; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Wastewater treatment plants (WWTP) are natural aggregators of pathogenic organisms due to the waste they treat. This study examined the fate of two bacterial indicators, fecal coliforms (FC) and Salmonella, and one viral indicator, Male-specific coliphages (MSCs), throughout an advanced WWTP. Samples were collected from various points in the WWTP from August 2011 to October 2012. Results show both bacteria and viruses preferentially partition into solids and significant reductions in both bacteria and viruses occur prior to final disposal. The total log removals of FC, Salmonella, and MSCs were 4.51, 5.17, and 6.19, respectively for the solids; and the total log removal of FC, Salmonella, and MSCs in liquids was 4.47, 5.16, and 3.62, respectively. This study provides the first holistic survey of bacteria and virus indicator fate in a WWTP. Furthermore, results herein demonstrate that current biosolids liming regulations may underestimate the level of viruses in Class B biosolids.Item ASSESSING THE FATE AND BIOAVAILABILITY OF HYDROPHOBIC ORGANIC POLLUTANTS IN AGRICULTURAL SOILS(2012) Almeida e Andrade, Natasha; Torrents, Alba; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Persistent organic pollutants have been the cause of concern for many decades; however, little information is available about their environmental fate. One goal of this work was to assess whether land application of biosolids represents a source of persistent organic pollutants to agricultural soils. To address this goal, we developed a methodology to quantify low levels of the flame retardants polybrominated diphenyl ethers (PBDEs) in biosolids and soils and conducted field studies to determine the fate and persistence of PBDEs upon the land application of biosolids. We found that biosolids can take up to one year to completely incorporate into the soil matrix after application and biosolids-bound chemicals are released during this time. PBDEs profiles in soils that receive biosolids applications are similar to PBDEs profiles in biosolids and both reflect commercial formulations of these flame retardants, indicating that biosolids are a source of these chemicals to soil. Residence time of these chemicals was reported for the first time and it was estimated at 16 yr. for the sum of BDE-47 and BDE-99. An abiotic methodology to assess bioavailability of aged soil residues was developed and results were compared to earthworms. The study illustrated that the polymer-based abiotic methodology can be used to assess the bioavailability of soil-bound hydrophobic organic chemicals to earthworms. Measured soil-polymer equilibrium concentration ratios of organic pollutants correlated strongly with earthworm bioaccumulation factors using the same soils. A laboratory protocol to introduce the concept of fugacity and bioavailability to undergraduate and graduate environmental science and engineering students was developed based on the methodology developed for research. The experiment provided an excellent opportunity for students to become familiar with the laboratory protocols and techniques for quantitative analysis as well as graphical analysis of data. The totality of this work improves knowledge of the fate of two classes of organic pollutants in soils. This work substantially adds information and understanding of chemical behavior to the general environmental engineering field. Although this unique experiment provided original and essential pieces of information, additional research is crucial to address the difficulties involved in assessing the environmental behavior of organic pollutants.Item Hyperspectral Reflectance as an Indicator of Foliar Nutrient Levels in Hybrid Poplar Clone OP-367 Grown on Biosolid Amended Soil(2009) Griffeth, Tommy; Felton, Gary; Biological Resources Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Trees of the genus Populus are fast growing trees that require considerable amounts of water and nutrients to meet physiological growth demands. The determination of correlations between hybrid poplar leaf spectral reflectance in the 325-1100 nm range, laboratory foliar analysis of leaf macronutrient and micronutrient concentrations, and leaf water potential datasets were analyzed using Full Cross-Validation and Test Set Models via the partial least squares (PLS) method of regression analysis. Based on an evaluation of the slope of the Predicted vs. Measured regression line, the root mean squared error (RMSE), and r-squared, the majority of the models constructed did not adequately model foliar concentrations from spectral data. However, the models for H, N, P, K, Cu and Al had values (slope of the Predicted vs. Measured regression line greater than 0.50 and r-squared values greater than 0.50 in at least one type of model) that warrant future study.